Seeds, Sowing Methods and Crop Stand Establishment
What the exam asks
Seeds, Sowing Methods and Crop Stand Establishment tests seed quality, germination, purity, seed rate, sowing methods and the factors that produce an adequate plant stand. Expect adjustment calculations and method-matching.
Core rules
- Good seed is genetically pure, physically clean, viable, free from pests and disease, and has high germination and vigour.
- Germination (%) is the proportion of pure seeds that produce normal seedlings; purity (%) is the proportion of the sample that is the desired seed.
- Seed rate depends on recommended plant population, 1000-grain weight, germination, purity and expected field survival.
- Methods: broadcasting is quick but uneven; line sowing or drilling gives uniform depth and spacing; dibbling places seeds in hills; transplanting raises seedlings first; ridge-furrow planting helps drainage and moisture management.
- Correct sowing depth and moisture are critical. Shallow sowing dries out; deep sowing exhausts seed reserves.
Worked example
A crop needs 100 kg ha−1 seed when germination is 90% and purity is 95%. Adjusted seed rate = 100 ÷ (0.90 × 0.95) = 100 ÷ 0.855 = 117 kg ha−1. Reasoning: the lot contains nonviable and off-type material, so more bulk is needed. If the farmer sows only 100 kg, the established stand will be about 85.5% of the target, other factors being equal.
Traps
High germination does not prove high purity; a cheap seed lot may need a higher rate. Do not increase sowing depth to compensate for dry surface soil without checking crop-specific limits. Broadcasting is not the same as drilling. Seed rate is not fixed for all varieties: seed size and target population matter.